Oracle White Paper—Working with Oracle Solaris ZFS Snapshots ... This guide is
intended to show a new user the capabilities of the snapshot feature of Oracle ...
An Oracle White Paper April 2010
Working with Oracle® Solaris ZFS Snapshots
Oracle White Paper—Working with Oracle Solaris ZFS Snapshots
Introduction.......................................................................................... 1
Oracle Solaris ZFS Snapshots: Overview ........................................... 2
Setting Up the File System .................................................................. 2
Taking a Snapshot............................................................................... 3
Rolling Back a Snapshot ..................................................................... 3
Copying Individual Files From a Snapshot .......................................... 4
Storing a Snapshot on Your System ................................................... 5
Sending a Snapshot to Another System.............................................. 5
For More Information ........................................................................... 6
Oracle White Paper—Working with Oracle Solaris ZFS Snapshots
Introduction This guide is intended to show a new user the capabilities of the snapshot feature of Oracle
®
Solaris ZFS. It describes the steps necessary to set up an Oracle Solaris ZFS file system, as well as how to create snapshots, use them for backup and restore purposes, and migrate them between systems. After reading this guide, the user will have a basic understanding of how snapshots can be integrated into system administration procedures.
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Oracle White Paper—Working with Oracle Solaris ZFS Snapshots
Oracle Solaris ZFS Snapshots: Overview An Oracle Solaris ZFS snapshot is a read-only copy of an Oracle Solaris ZFS file system or volume. Snapshots can be created almost instantly and initially consume no additional disk space within the pool. Snapshots are a valuable tool for system administrators needing to perform backups and other users needing to save the state of a file system at a particular point in time and possibly recreate it later on the same or another machine. It is also possible to extract individual files from a snapshot. These tasks can be performed with Oracle Solaris ZFS without the need for additional software. In this short guide, we take a look at the simple command syntax necessary to achieve these tasks.
Setting Up the File System The following steps explain how to set up the file system. 1.
First, we create a pool (which we call pool ) and display it. # zpool create -f pool c0d0s5 # zpool list
2.
NAME
SIZE
pool
3.11G
USED
AVAIL
CAP
HEALTH
ALTROOT
75K
3.11G
0%
ONLINE
-
Then we create a file system (called filesystem) in our pool and confirm that we have done so. # zfs create pool/filesystem # zfs list
3.
NAME
USED
AVAIL
REFER
MOUNTPOINT
pool
97.5K
3.06G
18K
/pool
pool/filesystem
18K
3.06G
18K
/pool/filesystem
Now to illustrate our example we fill the file system with some data. # cd /platform # du -h -s . 261M . # find . -print | cpio -pd /pool/filesystem 536032 blocks # zfs list NAME
USED
AVAIL
REFER
MOUNTPOINT
pool
206M
2.86G
19K
/pool
pool/filesystem
206M
2.86G
206M
/pool/filesystem
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Oracle White Paper—Working with Oracle Solaris ZFS Snapshots
We are now ready to start working with snapshots.
Taking a Snapshot 1.
Snapshots are named with the syntax pool/fs@something, where something can be a fairly arbitrary name, but ideally one that means something to the creator. # zfs snapshot pool/filesystem@thursday
2.
The snapshot is then visible using the zfs list command. # zfs list # zfs list
3.
NAME
USED
AVAIL
REFER
MOUNTPOINT
pool
262M
2.81G
19K
/pool
pool/filesystem
262M
2.81G
262M
/pool/filesystem
pool/filesystem@thursday
0
-
262M
-
However, the snapshot does not appear as a file system when using the df command. The reason it is hidden from normal Oracle Solaris utilities, such as ls, tar, cpio, and others, is to prevent the snapshot from appearing in backups. # df –h Filesystem
SIZE
USED
AVAIL
CAP
MOUNTED ON
pool
3.1G
19K
2.8G
1%
/pool
pool/filesystem
3.1G
262M
2.8G
9%
/pool/filesystem
Rolling Back a Snapshot 1.
Our snapshot can now be used as a recovery mechanism. First, we “accidentally” delete all the files in our file system. We see that the files have been removed and the size of the data reported for our file system has decreased appropriately. # cd /pool/filesystem # ls i86hvm i86pc i86xpv # rm -rf * # ls # df -h /pool/filesystem Filesystem
SIZE
USED
AVAIL
CAP
MOUNTED ON
pool/filesystem
3.1G
18K
2.8G
1%
/pool/filesystem
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Oracle White Paper—Working with Oracle Solaris ZFS Snapshots
2.
Rolling back the snapshot to restore all our missing files is trivial. We can see that the files have been returned and the space consumed again. # zfs list NAME
USED
AVAIL
REFER
MOUNTPOINT
pool
262M
2.81G
19K
/pool
pool/filesystem
262M
2.81G
18K
/pool/filesystem
-
262M
-
pool/filesystem@thursday 262M
# zfs rollback pool/filesystem@thursday # cd /pool/filesystem # ls i86hvm i86pc i86xpv # df -h /pool/filesystem Filesystem
SIZE
USED
AVAIL
CAP
MOUNTED ON
pool/filesystem
3.1G
262M
2.8G
9%
/pool/filesystem
Copying Individual Files From a Snapshot It is possible to copy individual files from a snapshot by changing into the hidden .zfs directory of the pool that has been snapped. # cd /pool # ls -la total 8 drwxr-xr-x
3 root root
3
Sep 11 15:33 .
drwxr-xr-x 23 root root
512 Sep 11 15:30 ..
drwxr-xr-x
2
2 root root
Sep 11 17:23 filesystem
# cd filesystem # ls -la total 6 drwxr-xr-x
2 root root
2 Sep 11 17:23 .
drwxr-xr-x
3 root root
3 Sep 11 15:33 ..
# cd .zfs # ls snapshot # cd snapshot # ls thursday # cd thursday # ls i86hvm i86pc i86xpv 4
Oracle White Paper—Working with Oracle Solaris ZFS Snapshots
Storing a Snapshot on Your System Storing snapshots on your system is a good practice for short-term storage as long as the snapshots are recreated regularly as data changes or the Oracle Solaris operating system is upgraded. Consider using an enterprise backup solution to save important data for long-term storage. In the following sequence of commands, we send the snapshot into a file and then compress it. It can then be retrieved from the file when required. This is also shown. # zfs send pool/filesystem@thursday > /var/tmp/thursday.snap # gzip -9 -v /var/tmp/thursday.snap # zfs create pool/thursday # gzip -d -c /var/tmp/thursday.snap.gz | zfs receive -F pool/thursday
Sending a Snapshot to Another System You can send the snapshot to another system and install it there as a usable file system. 1.
First, create a pool to receive the snapshot on the target system. otherhost# zpool create -f otherpool c0d0s7 otherhost# zpool list
2.
NAME
SIZE
USED
AVAIL
CAP
HEALTH
ALTROOT
otherpool
6.22G
75K
6.22G
0%
ONLINE
-
Then send the snapshot over the network and receive it into the pool using a combination of the zfs send and zfs receive commands and a network pipe. # zfs send pool/filesystem@thursday | ssh otherhost "/usr/sbin/zfs receive otherpool/myfs"
3.
The received snapshot is then visible in the pool on the other host. otherhost# zfs list NAME
USED
AVAIL
REFER
MOUNTPOINT
otherpool
262M
5.87G
19K
/otherpool
otherpool/myfs
262M
5.87G
262M
/otherpool/myfs
otherpool/myfs@thursday
0
-
262M
-
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Oracle White Paper—Working with Oracle Solaris ZFS Snapshots
For More Information There is more to the use of Oracle Solaris ZFS snapshots that we have not covered in this brief treatment. More comprehensive coverage of Oracle Solaris ZFS snapshots and clones, a related concept, are covered in the Solaris Oracle Solaris ZFS Administration Guide at Chapter 7: Working With Oracle Solaris ZFS Snapshots and Clones at http://docs.sun.com/app/docs/doc/819-5461. The Oracle Solaris ZFS manual is at http://docs.sun.com. Other sources of information are collected in Table 1. TABLE 1. WEB RESOURCES
The man pages for Oracle Solaris ZFS
http://docs.sun.com/app/docs/doc/819-2240/zfs-1m http://docs.sun.com/app/docs/doc/819-2240/zpool-1m
Oracle Solaris ZFS
http://www.oracle.com/us/products/servers-storage/storage/storagesoftware/031857.htm
Oracle Solaris ZFS Wiki
http://www.solarisinternals.com//wiki/index.php?title=Category:Oracle Solaris ZFS
OpenSolaris Oracle Solaris ZFS Community
http://www.opensolaris.org/os/community/zfs/
(The OpenSolaris Oracle Solaris ZFS manual is found here.) Opensolaris Mail Alias Archive
http://www.opensolaris.org/jive/forum.jspa?forumID=80
OpenSolaris advocacy group presentations
http://www.opensolaris.org/os/community/advocacy/os-presentations/
Search for Oracle Solaris ZFS
http://blogs.sun.com
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Working with Oracle Solaris ZFS Snapshots
Copyright © 2010, Oracle and/or its affiliates. All rights reserved.
April 2010
This document is provided for information purposes only and the contents hereof are subject to change without notice.
Author: Dominic Kay
This document is not warranted to be error-free, nor subject to any other warranties or conditions, whether expressed
Contributing Authors: Paul Eggleton, Cindy
orally or implied in law, including implied warranties and conditions of merchantability or fitness for a particular purpose.
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